advisory file locks in linux - do they work?
jgibson at spscommerce.com
Thu Apr 14 04:17:41 EST 2011
On 04/13/2011 11:45 AM, Bob Proulx wrote:
> You seem to think that all programs do file locking? Or perhaps you
> are aware that they do not but you think they /should/ use file
> locking and this is your way of lobbying to add it?
Whoa - Please don't start attacking. I had just read on some websites
that SFTP supported it (perhaps this was not OpenSSH), and I *thought* I
had it working on Solaris at one point. Guess not. Anyway it's good to
know this so I don't spend any more time trying to get it to work! :)
> Since you already know about the 'flock -c cmd' then you already know
> how to add this to sftp in your process.
Perhaps I wasn't very clear - we have clients connecting to us via SFTP
- We cannot reasonably expect them to know enough about UNIX/SFTP to do
the above, and many of the 3rd party programs they use are closed source
with limited feature sets. Instead I was hoping that it was possible
for the internal-sftp process to automatically lock incoming files. As
I have now learned, OpenSSH/SFTP does not support this natively.
However, we have had an internal developer add the functionality and so
far it seems to work.
> As such there is no need for file locking to be added to any
> particular program. You have the control to semaphore between any
> process that you wish to coordinate. This is much more flexible and
> powerful than creating an infinite number of infinitely large
> monolithic programs that contain all possible functionality.
OK - so is there a way to do this with the internal-sftp command while
using a chroot directory? I guess I'm not grokking how to do this on
the server-side without adding code or copying binaries to the user's
Anyway, thanks for you time.
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